Buidling Arduino Controller for Hamamatsu C12666MA mini-spectrometer

Projects Discussion and Showcase Science and Measurement
1

Currently, I'm in the process of attempting to build an arduino-based spectrometer with a Hamamatsu C12666MA as the light sensor that transmits all my data to the controller and plots it onto the serial plotter. To start, I've tried looking at a past project done on GitHub using the arduino spectrometer and trying out the code file provided to see how it worked. The code gave me rather strange outputs on the serial monitor and plotter. Here's the code below and I have attached a png of the serial plotter output.

The attached pic of the output on the serial plotter shows the graph when I shine a flashlight on the sensor and then turn it off. The graph's normal leveling area is at around 90 on the y-axis. Is this supposed to be the output? Is the software bugged? The demonstration video for this project uses the software Processing instead of Arduino to display the data. Any help with better understanding would be much appreciated. Thank you.

#define SPEC_GAIN A0
//#define SPEC_EOS NA
#define SPEC_ST A1
#define SPEC_CLK A2
#define SPEC_VIDEO A3
#define WHITE_LED A4
#define LASER_404 A5

#define SPEC_CHANNELS 256
uint16_t data[SPEC_CHANNELS];

void setup() {

//pinMode(SPEC_EOS, INPUT);
pinMode(SPEC_GAIN, OUTPUT);
pinMode(SPEC_ST, OUTPUT);
pinMode(SPEC_CLK, OUTPUT);

pinMode(WHITE_LED, OUTPUT);
pinMode(LASER_404, OUTPUT);
digitalWrite(WHITE_LED, LOW);
digitalWrite(LASER_404, LOW);

//digitalWrite(WHITE_LED, HIGH);
//digitalWrite(LASER_404, HIGH);

digitalWrite(SPEC_GAIN, HIGH);
digitalWrite(SPEC_ST, HIGH);
digitalWrite(SPEC_CLK, HIGH);
digitalWrite(SPEC_GAIN, HIGH); //LOW Gain
//digitalWrite(SPEC_GAIN, LOW); //High Gain

//Serial.begin(9600);
Serial.begin(115200);
}

void readSpectrometer()
{
//int delay_time = 35; // delay per half clock (in microseconds). This ultimately conrols the integration time.
int delay_time = 1; // delay per half clock (in microseconds). This ultimately conrols the integration time.
int idx = 0;
int read_time = 35; // Amount of time that the analogRead() procedure takes (in microseconds) (different micros will have different times)
int intTime = 100;
int accumulateMode = false;
int i;

// Step 1: start leading clock pulses
for (int i = 0; i < SPEC_CHANNELS; i++) {
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
}

// Step 2: Send start pulse to signal start of integration/light collection
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
digitalWrite(SPEC_ST, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
digitalWrite(SPEC_ST, HIGH);
delayMicroseconds(delay_time);

// Step 3: Integration time -- sample for a period of time determined by the intTime parameter
int blockTime = delay_time * 8;
long int numIntegrationBlocks = ((long)intTime * (long)1000) / (long)blockTime;
for (int i = 0; i < numIntegrationBlocks; i++) {
// Four clocks per pixel
// First block of 2 clocks -- measurement
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);

digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
}

// Step 4: Send start pulse to signal end of integration/light collection
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
digitalWrite(SPEC_ST, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
digitalWrite(SPEC_ST, HIGH);
delayMicroseconds(delay_time);

// Step 5: Read Data 2 (this is the actual read, since the spectrometer has now sampled data)
idx = 0;
for (int i = 0; i < SPEC_CHANNELS; i++) {
// Four clocks per pixel
// First block of 2 clocks -- measurement
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, LOW);

// Analog value is valid on low transition
if (accumulateMode == false) {
data[idx] = analogRead(SPEC_VIDEO);
} else {
data[idx] += analogRead(SPEC_VIDEO);
}
idx += 1;
if (delay_time > read_time) delayMicroseconds(delay_time - read_time); // Read takes about 135uSec

digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);

// Second block of 2 clocks -- idle
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
}

// Step 6: trailing clock pulses
for (int i = 0; i < SPEC_CHANNELS; i++) {
digitalWrite(SPEC_CLK, LOW);
delayMicroseconds(delay_time);
digitalWrite(SPEC_CLK, HIGH);
delayMicroseconds(delay_time);
}
}

void print_data()
{
for (int i = 0; i < SPEC_CHANNELS; i++)
{
Serial.print(data*);*

  • Serial.print(',');*
  • }*
  • Serial.print("\n");*
    }
    void loop()
    {
    // digitalWrite(LASER_404, HIGH);
    // readSpectrometer();
    // digitalWrite(LASER_404, LOW);
    // print_data();
    // delay(10);

// digitalWrite(WHITE_LED, HIGH);
// readSpectrometer();
// digitalWrite(WHITE_LED, LOW);
// print_data();
// delay(10);